Add: semi-working printf implementation

io.h

@@ -1,7 +1,10 @@
 #ifndef INCLUDE_IO_H
 #define INCLUDE_IO_H
 
+#include "stdint.h"
+
 void outb(unsigned short port, unsigned char data);
 unsigned char inb(unsigned short port);
+void x86_div64_32(uint64_t dividend, uint32_t divisor, uint64_t* quotientOut, uint32_t* remainderOut);
 
 #endif

io.s

@@ -12,3 +12,23 @@ inb:
   mov dx, [esp + 4]
   in al, dx
   ret
+
+global x86_div64_32
+
+x86_div64_32:
+  mov eax, [bp+8]
+  mov ecx, [bp+12]
+  xor edx, edx
+  div ecx
+
+  mov bx, [bp+16]
+  mov [bx+4], eax
+
+  mov eax, [bp+4]
+  div ecx
+
+  mov [bx], eax
+  mov bx, [bp+18]
+  mov [bx], edx
+
+  ret

kmain.c

@@ -8,7 +8,6 @@ int kmain(int retvalue)
   log("Kernel started", 2);
 
   clear();
-  puts("hello\nbrave\nnew\nworld");
+  printf("Formatted: %% %c %s %d\n", 'f', "Hello", 77);
-
   return retvalue;
 }

stdint.h

@@ -0,0 +1,20 @@
+#ifndef INCLUDE_STDINT_H
+#define INCLUDE_STDINT_H
+
+typedef signed char int8_t;
+typedef unsigned char uint8_t;
+
+typedef signed short int16_t;
+typedef unsigned short uint16_t;
+
+typedef signed long int int32_t;
+typedef unsigned long int uint32_t;
+
+typedef signed long long int int64_t;
+typedef unsigned long long int uint64_t;
+
+typedef uint8_t bool;
+#define true 1
+#define false 0
+
+#endif

stdio.c

@@ -1,6 +1,7 @@
 #include "io.h"
 #include "stdio.h"
 #include "string.h"
+#include "stdint.h"
 
 char* fb = (char *) 0x000B8000;
 const unsigned VGA_WIDTH = 80;
@@ -110,3 +111,191 @@ void puts(const char* str)
   }
 }
 
+void printf(const char* fmt, ...)
+{
+  int* argp = (int*) &fmt;
+  int state = PRINTF_STATE_START;
+  int length = PRINTF_LENGTH_START;
+  int radix = 10;
+  bool sign = false;
+
+  argp++;
+  while (*fmt)
+  {
+    switch(state) {
+    case PRINTF_STATE_START:
+      if (*fmt == '%')
+      {
+        state = PRINTF_STATE_LENGTH;
+      }
+      else {
+        putc(*fmt);
+      }
+      break;
+    case PRINTF_STATE_LENGTH:
+      if (*fmt == 'h')
+      {
+        length = PRINTF_LENGTH_SHORT;
+        state = PRINTF_STATE_SHORT;
+      }
+      else if (*fmt == 'l')
+      {
+        length = PRINTF_LENGTH_LONG;
+        state = PRINTF_STATE_LONG;
+      }
+      else {
+        goto PRINTF_STATE_SPEC_;
+      }
+      break;
+    case PRINTF_STATE_SHORT:
+      if (*fmt == 'h')
+      {
+        length = PRINTF_LENGTH_SHORT_SHORT;
+        state = PRINTF_STATE_SPEC;
+      }
+      else {
+        goto PRINTF_STATE_SPEC_;
+      }
+      break;
+    case PRINTF_STATE_LONG:
+      if (*fmt == 'l')
+      {
+        length = PRINTF_LENGTH_LONG_LONG;
+        state = PRINTF_STATE_SPEC;
+      }
+      else {
+        goto PRINTF_STATE_SPEC_;
+      }
+      break;
+    case PRINTF_STATE_SPEC:
+      PRINTF_STATE_SPEC_:
+        switch(*fmt)
+        {
+          case 'c':
+            putc((char)*argp);
+            argp++;
+            break;
+          case 's':
+            puts(*(const char **)argp);
+            argp++;
+            break;
+          case '%':
+            putc('%');
+            break;
+          case 'd':
+          case 'i':
+            radix = 10;
+            sign = true;
+            argp = printf_number(argp, length, sign, radix);
+            break;
+          case 'u':
+            radix = 10;
+            sign = false;
+            argp = printf_number(argp, length, sign, radix);
+            break;
+          case 'X':
+          case 'x':
+          case 'p':
+            radix = 16;
+            sign = false;
+            argp = printf_number(argp, length, sign, radix);
+            break;
+          case 'o':
+            radix = 8;
+            sign = false;
+            argp = printf_number(argp, length, sign, radix);
+            break;
+          default:
+            break;
+        }
+      state = PRINTF_STATE_START;
+      length = PRINTF_LENGTH_START;
+      radix = 10;
+      sign = false;
+      break;
+    }
+    fmt++;
+  }
+}
+
+const char charset[] = "0123456789abcdef";
+
+int* printf_number(int* argp, int length, bool sign, int radix)
+{
+  char buffer[32];
+  unsigned long long number;
+  int number_sign = 1;
+  int pos = 0;
+
+  switch(length)
+  {
+    case PRINTF_LENGTH_SHORT_SHORT:
+    case PRINTF_LENGTH_SHORT:
+    case PRINTF_LENGTH_START:
+      if (sign)
+      {
+        int n = *argp;
+        if (n < 0)
+        {
+          n = -n;
+          number_sign = -1;
+        }
+        number = (unsigned long long) n;
+      }
+      else {
+        number = *(unsigned int*) argp;
+      }
+      argp++;
+      break;
+    case PRINTF_LENGTH_LONG:
+      if (sign)
+      {
+        long int n = *(long int*)argp;
+        if (n < 0)
+        {
+          n = -n;
+          number_sign = -1;
+        }
+        number = (unsigned long long) n;
+      }
+      else {
+        number = *(unsigned long int*) argp;
+      }
+      argp += 2;
+      break;
+    case PRINTF_LENGTH_LONG_LONG:
+      if (sign)
+      {
+        long long int n = *(long long int*)argp;
+        if (n < 0)
+        {
+          n = -n;
+          number_sign = -1;
+        }
+        number = (unsigned long long) n;
+      }
+      else {
+        number = *(unsigned long long int*) argp;
+      }
+      argp += 4;
+      break;
+  }
+
+  do {
+    uint32_t rem;
+    x86_div64_32(number, radix, &number, &rem);
+    buffer[pos++] = charset[rem];
+  } while (number > 0);
+
+  if (sign && number_sign < 0)
+  {
+    buffer[pos++] = '-';
+  }
+
+  while (--pos >= 0)
+  {
+    putc(buffer[pos]);
+  }
+
+  return argp;
+}

stdio.h

@@ -1,6 +1,8 @@
 #ifndef INCLUDE_STDIO_H
 #define INCLUDE_STDIO_H
 
+#include "stdint.h"
+
 #define FB_GREEN      2
 #define FB_DARK_GREY  8
 
@@ -19,4 +21,19 @@ unsigned int getcolor(int x, int y);
 void scroll(int lines);
 void putc(char c);
 
+#define PRINTF_STATE_START 0
+#define PRINTF_STATE_LENGTH 1
+#define PRINTF_STATE_SHORT 2
+#define PRINTF_STATE_LONG 3
+#define PRINTF_STATE_SPEC 4
+
+#define PRINTF_LENGTH_START 0
+#define PRINTF_LENGTH_SHORT_SHORT 1
+#define PRINTF_LENGTH_SHORT 2
+#define PRINTF_LENGTH_LONG 3
+#define PRINTF_LENGTH_LONG_LONG 4
+
+void printf(const char* fmt, ...);
+int* printf_number(int* argp, int length, bool sign, int radix);
+
 #endif